This study presents the results of a multi-proxy analysis of a Holocene lacustrine sediment seque... more This study presents the results of a multi-proxy analysis of a Holocene lacustrine sediment sequence recovered from a small tundra lake in the central Canadian Arctic and links climatic variations there to the North Atlantic. Chironomid and pollen-based reconstructions of mean July air temperature (MJAT) document notable deviations at 9.3 ka and 8.2 ka. Chironomid-inferred July air temperature is depressed by 1.4 °C at 9.3 ka and 1.7 °C at 8.2 ka relative to the long-term chironomid-inferred Holocene average of 9.4 °C. These cooling events also correspond to an increase in Gramineae (Poaceae) and a decrease in Betula pollen, reflecting a decrease in the density of dwarf birch cover. Concurrent, abrupt increases in several diatom taxa, including aerophilic epiphytes, and Sphagnum indicate an expansion of moss habitats as a result of wetter conditions. The expression and timing of the cooling evidenced at TK2 during the early Holocene is consistent with abrupt climate events identifie...
... 1. Vegetation changes north of 55°N between the last glacial maximum, mid-Holocene, and prese... more ... 1. Vegetation changes north of 55°N between the last glacial maximum, mid-Holocene, and present Nancy H. Bigelow, 1 Linda B. Brubaker, 2 Mary E. Edwards, 3,4,5 Sandy P. Harrison, 6,7 I. Colin Prentice, 6 Patricia M. Anderson, 8 Andrei A. Andreev, 9 Patrick J. Bartlein, 10 ...
Continental-scale estimates of vegetation cover, including land-surface properties and biogeograp... more Continental-scale estimates of vegetation cover, including land-surface properties and biogeographic trends, reflect the response of plant species to climate change over the past millennia. These estimates can help assess the effectiveness of simulations of climate change using forward and inverse modelling approaches. With the advent of transient and contiguous time-slice palaeoclimate simulations, vegetation datasets with similar temporal qualities are desirable. We collated fossil pollen records for the period 21,000e0 cal yr BP (kyr cal BP; calibrated ages) for Europe and Asia north of 40 N, using extant databases and new data; we filtered records for adequate dating and sorted the nomenclature to conform to a consistent yet extensive taxon list. From this database we extracted pollen spectra representing 1000-year time-slices from 21 kyr cal BP to present and used the biomization approach to define the most likely vegetation biome represented. Biomes were mapped for the 22 time slices, and key plant functional types (PFTs, the constituents of the biomes) were tracked though time. An error matrix and index of topographic complexity clearly showed that the accuracy of pollen-based biome assignments (when compared with modern vegetation) was negatively correlated with topographic complexity, but modern vegetation was nevertheless effectively mapped by the pollen, despite moderate levels of misclassification for most biomes. The pattern at 21 ka is of herb-dominated biomes across the whole region. From the onset of deglaciation (17e18 kyr cal BP), some sites in Europe record forest biomes, particularly the south, and the proportion of forest biomes gradually increases with time through 14 kyr cal BP. During the same period, forest biomes and steppe or tundra biomes are intermixed across the central Asian mountains, and forest biomes occur in coastal Pacific areas. These forest biome
Continental-scale estimates of vegetation cover, including land-surface properties and biogeograp... more Continental-scale estimates of vegetation cover, including land-surface properties and biogeographic trends, reflect the response of plant species to climate change over the past millennia. These estimates can help assess the effectiveness of simulations of climate change using forward and inverse modelling approaches. With the advent of transient and contiguous time-slice palaeoclimate simulations, vegetation datasets with similar temporal qualities are desirable. We collated fossil pollen records for the period 21,000e0 cal yr BP (kyr cal BP; calibrated ages) for Europe and Asia north of 40 N, using extant databases and new data; we filtered records for adequate dating and sorted the nomenclature to conform to a consistent yet extensive taxon list. From this database we extracted pollen spectra representing 1000-year time-slices from 21 kyr cal BP to present and used the biomization approach to define the most likely vegetation biome represented. Biomes were mapped for the 22 time...
A set of 40 subfossil Scots pines (Pinus sylvestris L.) was sampled in small lakes beyond the mod... more A set of 40 subfossil Scots pines (Pinus sylvestris L.) was sampled in small lakes beyond the modernpine limit in the northwest Kola Peninsula, Russia. Radiocarbon dating suggests that the pine expanded north of its present-day limit between 7000 and 3500yr BP. The most extensive occurrence of pine forests was reconstructed between 6250 and 5750 yr BP. Numerous samples collected from trunks and stubs in situ clearly indicate lower lake levels between 6200 and 4400 yr BP. Living and 14C dated subfossil pine samples were analysed for the mean carbon, oxygen and hydrogen stable isotope composition of their wood cellulose. The mean δ13C, δ18O and δ2H values of the wood samples from the mid-Holocene time are C. 1.1%, 0.9% and lock, respectively - more positive than those of living trees in this region. These results suggest that the mid-Holocene climate in the region was warmer and drier than nowadays. The data agree with previous palynological, macrofossil and limnological studies from ...
Data obtained from the low-elevation Khibiny Mountains (ca. 6768°N; 3334°E) on the Kola Peninsu... more Data obtained from the low-elevation Khibiny Mountains (ca. 6768°N; 3334°E) on the Kola Peninsula, northwest Russia, indicate a period of exceptionally warm and dry conditions commenced at ca. AD 600 and was most pronounced between ca. AD 1000 and 1200. Warmer ...
ABSTRACT The broad and flat valley of the upper Dnister in western Ukraine is characterized by a ... more ABSTRACT The broad and flat valley of the upper Dnister in western Ukraine is characterized by a complex setting of ecotopes and a relatively natural state of floodplain dynamics. Excellent geo-archives–extended peat bogs and postglacial river terraces–document late Quaternary landscape evolution with special regard to changes in fluvial morphodynamics, vegetation and human impact. The terraces were studied by detailed geomorphological mapping as well as sedimentological and pedological analyses in connection with information from historical maps. Vegetation history was studied by palynological methods in combination with radiocarbon dating.Two Late Pleistocene (NT1 and NT2) and seven Holocene (H1–H7) river terraces are evident. The ecological transformation during the period of climatic warming at the end of the last glacial maximum (LGM) caused the most significant change in runoff and sediment load, as well as in the vegetation cover. The Dnister changed from a braided to a meandering river system. It was soon after the spreading of postglacial forests with an increasing dominance of broadleaved trees that the pollen diagrams reflected the first signs of anthropogene influence. Intensified agricultural land use since the Iron Age is mirrored in the increasing amount of herbaceous pollen as well as the rise of fluvial sediment redeposition. Modern hydraulic engineering on the Dnister has caused visible transformations. Because of these impacts, the stability of the upper Dnister ecosystem has decreased significantly and is now highly sensitive to environmental change.
The broad and flat valley of the upper Dnister in western Ukraine is characterized by a complex s... more The broad and flat valley of the upper Dnister in western Ukraine is characterized by a complex setting of ecotopes and a relatively natural state of floodplain dynamics. Excellent geo-archives–extended peat bogs and postglacial river terraces–document late Quaternary landscape evolution with special regard to changes in fluvial morphodynamics, vegetation and human impact. The terraces were studied by detailed geomorphological mapping as well as sedimentological and pedological analyses in connection with information from historical maps. Vegetation history was studied by palynological methods in combination with radiocarbon dating.Two Late Pleistocene (NT1 and NT2) and seven Holocene (H1–H7) river terraces are evident. The ecological transformation during the period of climatic warming at the end of the last glacial maximum (LGM) caused the most significant change in runoff and sediment load, as well as in the vegetation cover. The Dnister changed from a braided to a meandering riv...
Data obtained from the low-elevation Khibiny Mountains (ca. 6768°N; 3334°E) on the Kola Peninsu... more Data obtained from the low-elevation Khibiny Mountains (ca. 6768°N; 3334°E) on the Kola Peninsula, northwest Russia, indicate a period of exceptionally warm and dry conditions commenced at ca. AD 600 and was most pronounced between ca. AD 1000 and 1200. Warmer ...
In terrestrial records from Central and Eastern Europe the end of the Last Interglacial seems to ... more In terrestrial records from Central and Eastern Europe the end of the Last Interglacial seems to be characterized by evident climatic and environmental instabilities recorded by geochemical and vegetation indicators. The transition (MIS 5e/5d) from the Last Interglacial (Eemian, Mikulino) to the Early Last Glacial (Early Weichselian, Early Valdai) is marked by at least two warming events as observed in geochemical data on the lake sediment profiles of Central (Gröbern, Neumark–Nord, Klinge) and of Eastern Europe (Ples). Results of palynological studies of all these sequences indicate simultaneously a strong increase of environmental oscillations during the very end of the Last Interglacial and the beginning of the Last Glaciation. This paper discusses possible correlations of these events between regions in Central and Eastern Europe. The pronounced climate and environment instability during the interglacial/glacial transition could be consistent with the assumption that it is about...
This study presents the results of a multi-proxy analysis of a Holocene lacustrine sediment seque... more This study presents the results of a multi-proxy analysis of a Holocene lacustrine sediment sequence recovered from a small tundra lake in the central Canadian Arctic and links climatic variations there to the North Atlantic. Chironomid and pollen-based reconstructions of mean July air temperature (MJAT) document notable deviations at 9.3 ka and 8.2 ka. Chironomid-inferred July air temperature is depressed by 1.4 °C at 9.3 ka and 1.7 °C at 8.2 ka relative to the long-term chironomid-inferred Holocene average of 9.4 °C. These cooling events also correspond to an increase in Gramineae (Poaceae) and a decrease in Betula pollen, reflecting a decrease in the density of dwarf birch cover. Concurrent, abrupt increases in several diatom taxa, including aerophilic epiphytes, and Sphagnum indicate an expansion of moss habitats as a result of wetter conditions. The expression and timing of the cooling evidenced at TK2 during the early Holocene is consistent with abrupt climate events identifie...
... 1. Vegetation changes north of 55°N between the last glacial maximum, mid-Holocene, and prese... more ... 1. Vegetation changes north of 55°N between the last glacial maximum, mid-Holocene, and present Nancy H. Bigelow, 1 Linda B. Brubaker, 2 Mary E. Edwards, 3,4,5 Sandy P. Harrison, 6,7 I. Colin Prentice, 6 Patricia M. Anderson, 8 Andrei A. Andreev, 9 Patrick J. Bartlein, 10 ...
Continental-scale estimates of vegetation cover, including land-surface properties and biogeograp... more Continental-scale estimates of vegetation cover, including land-surface properties and biogeographic trends, reflect the response of plant species to climate change over the past millennia. These estimates can help assess the effectiveness of simulations of climate change using forward and inverse modelling approaches. With the advent of transient and contiguous time-slice palaeoclimate simulations, vegetation datasets with similar temporal qualities are desirable. We collated fossil pollen records for the period 21,000e0 cal yr BP (kyr cal BP; calibrated ages) for Europe and Asia north of 40 N, using extant databases and new data; we filtered records for adequate dating and sorted the nomenclature to conform to a consistent yet extensive taxon list. From this database we extracted pollen spectra representing 1000-year time-slices from 21 kyr cal BP to present and used the biomization approach to define the most likely vegetation biome represented. Biomes were mapped for the 22 time slices, and key plant functional types (PFTs, the constituents of the biomes) were tracked though time. An error matrix and index of topographic complexity clearly showed that the accuracy of pollen-based biome assignments (when compared with modern vegetation) was negatively correlated with topographic complexity, but modern vegetation was nevertheless effectively mapped by the pollen, despite moderate levels of misclassification for most biomes. The pattern at 21 ka is of herb-dominated biomes across the whole region. From the onset of deglaciation (17e18 kyr cal BP), some sites in Europe record forest biomes, particularly the south, and the proportion of forest biomes gradually increases with time through 14 kyr cal BP. During the same period, forest biomes and steppe or tundra biomes are intermixed across the central Asian mountains, and forest biomes occur in coastal Pacific areas. These forest biome
Continental-scale estimates of vegetation cover, including land-surface properties and biogeograp... more Continental-scale estimates of vegetation cover, including land-surface properties and biogeographic trends, reflect the response of plant species to climate change over the past millennia. These estimates can help assess the effectiveness of simulations of climate change using forward and inverse modelling approaches. With the advent of transient and contiguous time-slice palaeoclimate simulations, vegetation datasets with similar temporal qualities are desirable. We collated fossil pollen records for the period 21,000e0 cal yr BP (kyr cal BP; calibrated ages) for Europe and Asia north of 40 N, using extant databases and new data; we filtered records for adequate dating and sorted the nomenclature to conform to a consistent yet extensive taxon list. From this database we extracted pollen spectra representing 1000-year time-slices from 21 kyr cal BP to present and used the biomization approach to define the most likely vegetation biome represented. Biomes were mapped for the 22 time...
A set of 40 subfossil Scots pines (Pinus sylvestris L.) was sampled in small lakes beyond the mod... more A set of 40 subfossil Scots pines (Pinus sylvestris L.) was sampled in small lakes beyond the modernpine limit in the northwest Kola Peninsula, Russia. Radiocarbon dating suggests that the pine expanded north of its present-day limit between 7000 and 3500yr BP. The most extensive occurrence of pine forests was reconstructed between 6250 and 5750 yr BP. Numerous samples collected from trunks and stubs in situ clearly indicate lower lake levels between 6200 and 4400 yr BP. Living and 14C dated subfossil pine samples were analysed for the mean carbon, oxygen and hydrogen stable isotope composition of their wood cellulose. The mean δ13C, δ18O and δ2H values of the wood samples from the mid-Holocene time are C. 1.1%, 0.9% and lock, respectively - more positive than those of living trees in this region. These results suggest that the mid-Holocene climate in the region was warmer and drier than nowadays. The data agree with previous palynological, macrofossil and limnological studies from ...
Data obtained from the low-elevation Khibiny Mountains (ca. 6768°N; 3334°E) on the Kola Peninsu... more Data obtained from the low-elevation Khibiny Mountains (ca. 6768°N; 3334°E) on the Kola Peninsula, northwest Russia, indicate a period of exceptionally warm and dry conditions commenced at ca. AD 600 and was most pronounced between ca. AD 1000 and 1200. Warmer ...
ABSTRACT The broad and flat valley of the upper Dnister in western Ukraine is characterized by a ... more ABSTRACT The broad and flat valley of the upper Dnister in western Ukraine is characterized by a complex setting of ecotopes and a relatively natural state of floodplain dynamics. Excellent geo-archives–extended peat bogs and postglacial river terraces–document late Quaternary landscape evolution with special regard to changes in fluvial morphodynamics, vegetation and human impact. The terraces were studied by detailed geomorphological mapping as well as sedimentological and pedological analyses in connection with information from historical maps. Vegetation history was studied by palynological methods in combination with radiocarbon dating.Two Late Pleistocene (NT1 and NT2) and seven Holocene (H1–H7) river terraces are evident. The ecological transformation during the period of climatic warming at the end of the last glacial maximum (LGM) caused the most significant change in runoff and sediment load, as well as in the vegetation cover. The Dnister changed from a braided to a meandering river system. It was soon after the spreading of postglacial forests with an increasing dominance of broadleaved trees that the pollen diagrams reflected the first signs of anthropogene influence. Intensified agricultural land use since the Iron Age is mirrored in the increasing amount of herbaceous pollen as well as the rise of fluvial sediment redeposition. Modern hydraulic engineering on the Dnister has caused visible transformations. Because of these impacts, the stability of the upper Dnister ecosystem has decreased significantly and is now highly sensitive to environmental change.
The broad and flat valley of the upper Dnister in western Ukraine is characterized by a complex s... more The broad and flat valley of the upper Dnister in western Ukraine is characterized by a complex setting of ecotopes and a relatively natural state of floodplain dynamics. Excellent geo-archives–extended peat bogs and postglacial river terraces–document late Quaternary landscape evolution with special regard to changes in fluvial morphodynamics, vegetation and human impact. The terraces were studied by detailed geomorphological mapping as well as sedimentological and pedological analyses in connection with information from historical maps. Vegetation history was studied by palynological methods in combination with radiocarbon dating.Two Late Pleistocene (NT1 and NT2) and seven Holocene (H1–H7) river terraces are evident. The ecological transformation during the period of climatic warming at the end of the last glacial maximum (LGM) caused the most significant change in runoff and sediment load, as well as in the vegetation cover. The Dnister changed from a braided to a meandering riv...
Data obtained from the low-elevation Khibiny Mountains (ca. 6768°N; 3334°E) on the Kola Peninsu... more Data obtained from the low-elevation Khibiny Mountains (ca. 6768°N; 3334°E) on the Kola Peninsula, northwest Russia, indicate a period of exceptionally warm and dry conditions commenced at ca. AD 600 and was most pronounced between ca. AD 1000 and 1200. Warmer ...
In terrestrial records from Central and Eastern Europe the end of the Last Interglacial seems to ... more In terrestrial records from Central and Eastern Europe the end of the Last Interglacial seems to be characterized by evident climatic and environmental instabilities recorded by geochemical and vegetation indicators. The transition (MIS 5e/5d) from the Last Interglacial (Eemian, Mikulino) to the Early Last Glacial (Early Weichselian, Early Valdai) is marked by at least two warming events as observed in geochemical data on the lake sediment profiles of Central (Gröbern, Neumark–Nord, Klinge) and of Eastern Europe (Ples). Results of palynological studies of all these sequences indicate simultaneously a strong increase of environmental oscillations during the very end of the Last Interglacial and the beginning of the Last Glaciation. This paper discusses possible correlations of these events between regions in Central and Eastern Europe. The pronounced climate and environment instability during the interglacial/glacial transition could be consistent with the assumption that it is about...
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Papers by Konstantin Kremenetski